1. Field of the Invention
The present invention relates to a multi charged particle beam writing apparatus and a multi charged particle beam writing method.
2. Description of Related Art
The lithography technique that advances microminiaturization of semiconductor devices is extremely important as being a unique process whereby patterns are formed in the semiconductor manufacturing. In recent years, with high integration of LSI, the line width (critical dimension) required for semiconductor device circuits is decreasing year by year. The electron beam (EB) writing technique, which intrinsically has excellent resolution, is used for writing or “drawing” a pattern on a wafer, etc. with electron beams.
For example, there is a writing apparatus using multiple beams (multi-beams). Since it is possible for a multi-beam writing apparatus to perform irradiation with many beams at one time, throughput can be greatly increased compared with the case of writing using one electron beam.
FIG. 15 shows a part of the structure of a writing apparatus of a multi-beam system. In such a writing apparatus of a multi-beam system, as shown in FIG. 15, multi-beams 502 are formed by letting an electron beam 500 emitted from an electron gun assembly 501 pass through a mask (multi-beam forming aperture) 510 having a plurality of holes, for example. Each of the formed multiple beams is blanking-controlled by a blanking deflection electrode array (blanker array) 512 arranged close to the mask 510, and each of beams at the downstream side, which is not blocked by the aperture, is reduced by an optical system and deflected by a deflector so as to be irradiated on a desired position on a target object or “sample” (refer to, e.g., Japanese Patent Application Laid-open (JP-A) No. 2006-261342).
Conventionally, in such a writing apparatus of a multi-beam system, a mask (multi-beam forming aperture) with a plurality of holes for forming multiple beams and a blanking deflection electrode array (blanker array) for respectively performing blanking control of each beam are closely arranged. Therefore, there is a problem in that electrons scattered by the multi-beam forming aperture flow into the blanking deflection electrode array, and then make an insulator portion charged or promote contamination 520.